To implement DTN (Delay-Tolerant Networking) architectures in ns3, we need to follow several steps. Because, DTN protocols will not directly support on ns3 like bundle protocol. So, for this process custom application is necessary to simulate the DTN functionality. And also we need to create a network that can handle the intermittent connectivity and long delays by using the intermediate nodes and also including the data storing, carrying and forwarding. The following steps will guide on how to implement DTN architectures using ns3.
Step-by-step guide on implementing DTN Architectures:
Step 1: Set Up the Simulation Environment
Make sure ns3 installed on the system.
Step 2: Create the Network Topology
Create a basic network topology using ns3 with multiple nodes. For this example, we will create a scenario where Node A sends data to Node C via Node B, simulating the DTN store-carry-forward mechanism.
Step 3: Define the DTN Application
Create a custom DTN application that implements the DTN store-carry-forward functionality.
Step 4: Write the Script
An example given on how to create and configure a network topology in ns3 with a basic DTN application:
- Create a New File:
- Save the following script as dtn-architecture.cc in the scratch directory of the ns3 installation.
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/point-to-point-module.h”
#include “ns3/applications-module.h”
#include “ns3/mobility-module.h”
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“DtnArchitectureExample”);
class DtnApplication : public Application
{
public:
DtnApplication ();
virtual ~DtnApplication ();
void Setup (Ptr<Socket> socket, Address address, uint32_t packetSize, uint32_t nPackets, Time interPacketInterval);
void AddIntermediateNode (Ptr<Node> node);
protected:
virtual void StartApplication (void);
virtual void StopApplication (void);
private:
void SendPacket ();
void ReceivePacket (Ptr<Socket> socket);
void ForwardBundles ();
Ptr<Socket> m_socket;
Address m_peer;
uint32_t m_packetSize;
uint32_t m_nPackets;
Time m_interval;
uint32_t m_sent;
std::vector<Ptr<Packet>> m_bundleBuffer;
std::vector<Ptr<Node>> m_intermediateNodes;
EventId m_forwardEvent;
};
DtnApplication::DtnApplication ()
: m_socket (0),
m_packetSize (0),
m_nPackets (0),
m_sent (0)
{
}
DtnApplication::~DtnApplication ()
{
m_socket = 0;
}
void
DtnApplication::Setup (Ptr<Socket> socket, Address address, uint32_t packetSize, uint32_t nPackets, Time interPacketInterval)
{
m_socket = socket;
m_peer = address;
m_packetSize = packetSize;
m_nPackets = nPackets;
m_interval = interPacketInterval;
}
void
DtnApplication::AddIntermediateNode (Ptr<Node> node)
{
m_intermediateNodes.push_back (node);
}
void
DtnApplication::StartApplication (void)
{
m_socket->Bind ();
m_socket->Connect (m_peer);
m_socket->SetRecvCallback (MakeCallback (&DtnApplication::ReceivePacket, this));
SendPacket ();
}
void
DtnApplication::StopApplication (void)
{
if (m_socket)
{
m_socket->Close ();
}
Simulator::Cancel (m_forwardEvent);
}
void
DtnApplication::SendPacket ()
{
Ptr<Packet> packet = Create<Packet> (m_packetSize);
m_bundleBuffer.push_back (packet);
if (++m_sent < m_nPackets)
{
Simulator::Schedule (m_interval, &DtnApplication::SendPacket, this);
}
}
void
DtnApplication::ReceivePacket (Ptr<Socket> socket)
{
Ptr<Packet> packet = socket->Recv ();
m_bundleBuffer.push_back (packet);
if (socket->GetNode () == m_intermediateNodes.back ())
{
m_socket->Send (packet);
}
}
void
DtnApplication::ForwardBundles ()
{
for (auto &bundle : m_bundleBuffer)
{
for (auto &node : m_intermediateNodes)
{
Ptr<Socket> socket = Socket::CreateSocket (node, UdpSocketFactory::GetTypeId ());
socket->Bind ();
socket->Connect (InetSocketAddress (Ipv4Address::ConvertFrom (m_peer), 9));
socket->Send (bundle);
}
}
m_bundleBuffer.clear ();
m_forwardEvent = Simulator::Schedule (Seconds (10), &DtnApplication::ForwardBundles, this); // Schedule forwarding every 10 seconds
}
int main (int argc, char *argv[])
{
CommandLine cmd;
cmd.Parse (argc, argv);
NodeContainer nodes;
nodes.Create (3); // A, B, C
PointToPointHelper pointToPoint;
pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“5Mbps”));
pointToPoint.SetChannelAttribute (“Delay”, StringValue (“2ms”));
NetDeviceContainer devicesAB, devicesBC;
devicesAB = pointToPoint.Install (nodes.Get (0), nodes.Get (1)); // A to B
devicesBC = pointToPoint.Install (nodes.Get (1), nodes.Get (2)); // B to C
InternetStackHelper stack;
stack.Install (nodes);
Ipv4AddressHelper address;
address.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfacesAB = address.Assign (devicesAB);
address.SetBase (“10.1.2.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfacesBC = address.Assign (devicesBC);
// Set up mobility
MobilityHelper mobility;
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (nodes);
nodes.Get (0)->GetObject<MobilityModel> ()->SetPosition (Vector (0.0, 0.0, 0.0));
nodes.Get (1)->GetObject<MobilityModel> ()->SetPosition (Vector (50.0, 0.0, 0.0));
nodes.Get (2)->GetObject<MobilityModel> ()->SetPosition (Vector (100.0, 0.0, 0.0));
// Set up applications
uint32_t packetSize = 1024;
uint32_t nPackets = 10;
Time interPacketInterval = Seconds (1.0);
Ptr<Socket> recvSink = Socket::CreateSocket (nodes.Get (2), UdpSocketFactory::GetTypeId ());
InetSocketAddress local = InetSocketAddress (Ipv4Address::GetAny (), 9);
recvSink->Bind (local);
recvSink->SetRecvCallback (MakeCallback (&DtnApplication::ReceivePacket, DynamicCast<DtnApplication> (nodes.Get (2)->GetApplication (0))));
Ptr<Socket> source = Socket::CreateSocket (nodes.Get (0), UdpSocketFactory::GetTypeId());
Ptr<DtnApplication> app = CreateObject<DtnApplication> ();
app->Setup (source, InetSocketAddress (interfacesBC.GetAddress (1), 9), packetSize, nPackets, interPacketInterval);
app->AddIntermediateNode (nodes.Get (1)); // B as intermediate node
nodes.Get (0)->AddApplication (app);
app->SetStartTime (Seconds (2.0));
app->SetStopTime (Seconds (20.0));
app->ForwardBundles(); // Start the forwarding process
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Explanation:
- Create Nodes and Network:
- Create three nodes (A, B, and C) and connect them using point-to-point links.
- Install the Internet stack on the nodes.
- Assign IP addresses to the devices.
- Define DTN Application:
- Create a DtnApplication class that implements the DTN store-carry-forward mechanism.
- The application sends packets, stores them in a buffer, and forwards them to intermediate nodes.
- The SendPacket function creates packets and adds them to the bundle buffer.
- The ReceivePacket function handles incoming packets and stores them in the buffer.
- The ForwardBundles function forwards the bundles to the next hop or the destination at scheduled intervals.
- Install and Configure the Application:
- Create sockets for sending and receiving.
- Install the DtnApplication on the source node (A).
- Configure the application with the necessary parameters, such as packet size, number of packets, and inter-packet interval.
- Add the intermediate node (B) to the application.
- Start the forwarding process.
- Run the Simulation:
- Schedule the start and stop times for the application.
- Run the simulation and log the results.
Step 4: Compile and Run the Script
- Save the script as dtn-architecture.cc in the scratch directory of ns3 installation.
- Compile the script using the following commands:
./waf configure
./waf build
./waf –run dtn-architecture
Step 5: Analyze the Results
We can analyze the results by looking at the logs to verify the behavior of the DTN application after running the simulation.
Over all, the example and steps clearly explains about the implementation process of DTN architecture by creating a network which can handle all the data stored, carried, and forwarded for simulation process.
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